oa A Comparison of 2D and 3D IP from Copper Hill NSW

This paper compares the results from 2D inversion of 2D data, 3D inversion of 2D data and 3D inversion of 3D data from a 3D pole-dipole MIMDAS IP survey conducted near Copper Hill NSW.

Six 1.5km lines were laid out over the area of interest at 200m spacings. Data were collected using ‘pole-dipole’ geometry with 100m dipoles. All receiver stations on all lines were read simultaneously for each transmitter station.

Data were processed using standard (proprietary) MIMDAS processing. 2D data were inverted using UBC’s dcip2d software while 2D and 3D data were inverted using UBC’s dcip3d code ported to an NEC SX-5 supercomputer. For the 3D models, resistivities were determined by inversion of primary voltages while secondary voltages, after Time Domain Cole-Cole Inversion, were inverted for the IP model. All errors were based linearly upon observational errors.

Results highlight the differences between inversion models for the two datasets. In particular, the models demonstrate the greater resolution of the 3D survey and the restricted ability of 2D surveys to define boundaries subparallel to the survey lines is emphasized.